1. Field of the Invention
The present invention is related to a torsional MEMS device, and particularly, to a torsional MEMS device of adjustable resonant frequency.
2. Description of the Prior Art
In the past years, MEMS devices have been developed for miniaturization of mechanical devices. The MEMS devices are manufactured by processes used for forming integrated circuits. Typical MEMS devices, including micro-gears, micro-levers, and micro-valves, are operated in company with related electrical circuits to form several devices, such as accelerometers, pressure and chemical sensors, and actuators.
MEMS devices are formed using silicon as material. The silicon materials are processed by several semiconductor processes to form the structures of the MEMS devices. For example, torsional MEMS devices use hinge as the motive structure. The figure of the hinge is a major factor for determining the resonant frequency of the torsional MEMS devices. In addition, resonant frequency is also a major factor for determining the performance of the torsional MEMS device. Therefore, several processes are performed to manufacture the hinge and to modify the hinge having desirable resonant frequency. It is appreciated that demands of the resonant frequency of the torsional MEMS device is getting more accurate, and it is getting difficult to form the hinge of determined shape by a simple lithography process or an etch process at present. As a result, applicant provides a torsional MEMS device which the resonant frequency of the torsional MEMS device may be adjusted to overcome the limitation resulted from the present processes for forming the conventional torsional MEMS devices. Additionally, the resonant frequency of the torsional MEMS device of the present invention may be adjusted after the manufacturing processes to fulfill the standard resonant frequency of the product.